fix: missing OwnInfo import

[truenicoco]

get_self() cannot be awaited without this fix:

   File "/venv/lib/python3.11/site-packages/maufbapi/http/api.py", line 344, in get_self
     fields = ",".join(field.name for field in attr.fields(OwnInfo))
                                                           ^^^^^^^
 NameError: name 'OwnInfo' is not defined